Bad charge controller?

Options
FirefliesNfrogs
FirefliesNfrogs Registered Users Posts: 2
in Solar Beginners Corner #1
Hello, this is my first post and I am looking for help. I had recently bought the 100 W solar panel kit on Amazon. It came with a charge controller. I had purchased 2. 6V Duracell golf cart batteries. During the daytime my charge controller says it is charging about 12.5 V and my batteries eventually charge up to 13 V. But after the sun goes down my batteries charge goes down to 12.5, 12.3 V. I do not have my inverter hooked up to my battery bank. I am very interested in solar panels and help to make a Solar battery bank. I just cannot understand why my batteries are not holding a charge. My batteries are new.
· Share on Twitter

Comments

  • BB.
    BB. Super Moderators, Administrators Posts: 33,439 admin
    #2
    Options
    Re: Bad charge controller?

    Welcome to the forum FFNF!

    Ok... Guessing that you might have gotten the Renogy 100 watt panel + 30 amp charge controller. The panel should be fine. The rated current should be around:
    Renogy 100W Monocrystalline Solar Panel
    Maximum Power: 100W
    Optimum Operating Voltage (Vmp): 18.9V
    Optimum Operating Current (Imp): 5.29A

    Don't know anything about the charge controller--But lets assume it is working.

    Next, if these are 6 volt ~ 200 AH lead acid batteries. Lets call 12.3 volts about 1/2 charge (for round numbers).

    This is winter, using the SolarElectricHandbook for Tulsa OK, fixed array:
    [h=3]Tulsa
    Average Solar Insolation figures[/h] Measured in kWh/m2/day onto a solar panel set at a 54° angle (from Vertical):
    (For best year-round performance)

    Jan
    Feb
    Mar
    Apr
    May
    Jun


    3.61

    4.01

    4.74

    5.20

    5.22

    5.37



    Jul
    Aug
    Sep
    Oct
    Nov
    Dec


    5.84

    5.62

    5.28

    4.75

    3.73

    3.36



    With a PWM controller the maximum charging current Imp~5.29 Amps. With 4.01 hours of sun average for February:

    5.29 amps * 4.01 hours of sun = 21.2 AH of current per day

    The battery:

    200 AH * 50% = 100 AH
    100 AH / 21.2 AH per day = 4.71 days of average sun for February

    The 200 AH battery bank with ~5 amps of charging current is about the minimum size solar panel we would recommend for charging a lead acid battery. That is OK for weekend/seasonal usage... For daily usage, a 10% to 13%+ solar array would be nice.

    If you would like to learn more about your system and how it is operating, you might want to look at getting a DC Current Clamp Digital Multi Meter, such as this one from Sears (pretty inexpensive and "good enough" for our needs).

    You should also get a decent Glass Hydrometer to measure the specific gravity of your battery bank (assuming flooded cell). If you want a really nice Hydrometer, take a look at this one.

    Read about batteries... They are the "critical part" of your system. If you leave it set at less than ~75% state of charge, it will sulfate faster (and could be dead within 6 months).

    http://www.windsun.com/Batteries/Battery_FAQ.htm
    http://www.batteryfaq.org/
    http://batteryuniversity.com/

    Electrically speaking, you want to see the charging voltage of the battery to be held at 2-6 hours or so at around 14.4 to 14.8 volts to be fully charged.

    -Bill
    Near San Francisco California: 3.5kWatt Grid Tied Solar power system+small backup genset
    · Share on Twitter
  • 706jim
    706jim Solar Expert Posts: 514 ✭✭✭✭
    #3
    Options
    Re: Bad charge controller?
    FirefliesNfrogs wrote: »
    Hello, this is my first post and I am looking for help. I had recently bought the 100 W solar panel kit on Amazon. It came with a charge controller. I had purchased 2. 6V Duracell golf cart batteries. During the daytime my charge controller says it is charging about 12.5 V and my batteries eventually charge up to 13 V. But after the sun goes down my batteries charge goes down to 12.5, 12.3 V. I do not have my inverter hooked up to my battery bank. I am very interested in solar panels and help to make a Solar battery bank. I just cannot understand why my batteries are not holding a charge. My batteries are new.

    I used golf cart batteries for years. (Mine were set up for 24 volts, so compare half of my readings here).

    I would float the batteries at 27.0 volts (or 13.5 for your case) and a few hours after the sun went down, the voltage would drop to about 25.0 (or 12.5 in your case) even if there was zero load on them.

    I don't think there's anything wrong with your batteries although the charge controller could probably have a higher cutoff point if it is adjustable.
    Island cottage solar system with 2500 watts of panels, 1kw facing southeast 1.3kw facing southwest 170watt ancient Arco's facing south. All panels in parallel for a 24 volt system. Trace DR1524 MSW inverter, Outback Flexmax 80 MPPT charge controller 8 Trojan L16's. Insignia 11.5 cubic foot electric fridge. My 30th year.
    · Share on Twitter
  • FirefliesNfrogs
    FirefliesNfrogs Registered Users Posts: 2
    #4
    Options
    Re: Bad charge controller?

    Thank you all for the help.
    · Share on Twitter

Categories